You can change or rename the new account name for a user in UNIX/Linux operating system. The account name must begin with an alphabetic character and the rest of the string should be from the POSIX portable character class. Nothing else is changed.
1. To rename
# sudo usermod -l <new-name> <current-old-name>
Additional note:
usermod -l will not allow you to change the name of a user who is logged in.
